Removing sod from a stacking conveyor

ABSTRACT

Sod harvester stacking head and stacking conveyor configurations can increase the rate at which sod can be harvested. The movement of the stacking head and/or the stacking conveyor can be controlled to maximize the rate at which the stacking head can remove sod from the stacking conveyor. A stacking head can employ multiple pick up positions. A stacking conveyor may also advance sod for pick up at varying rates. A stacking head may include a pivoting connection to allow the stacking head to rotate around a pivot during a pick up operation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.13/851,418 (the '418 application), titled Electrically Operated TurfStacking System For Sod Harvesting Machine, which was filed on Mar. 27,2013 and is incorporated herein by reference. The '418 applicationdescribes a stacking head that is suitable for use in implementing someembodiments of the present invention.

This application is also related to U.S. patent application Ser. No.13/851,402 (the '402 application), titled Conveyor System ForControlling Spacing Between Sod Slabs, which was filed on Mar. 27, 2013and is incorporated herein by reference. The '402 application describesa conveyor system that can be used in some embodiments of the presentinvention.

BACKGROUND

Turf grass (sod) is a living organism that must be handled properly toensure its survival when it is removed from one location andtransplanted to another. Sod is generally harvested using largemachinery that cuts slabs of sod from the soil. Typically, a sodharvester employs one or more inclined conveyors to elevate the sod fromthe ground to a horizontal conveyor. A stacking head is then used topick up the sod from the horizontal conveyor and stack it on a pallet.

Two general types of harvesters exist: slab harvesters; and rollharvesters. A roll harvester forms the slabs of sod into rolls which arethen accumulated on the horizontal conveyor for pick up. A slabharvester, on the other hand, directly stacks the slabs in their flatform. With either type of harvester, the speed at which the harvestercan remove sod from the horizontal conveyor and stack it oftentimes isthe controlling factor that determines how fast the harvester canoperate.

BRIEF SUMMARY

The present invention extends to sod harvester stacking head andstacking conveyor configurations as well as to systems, methods, andcomputer program products configured to control the movement of thestacking head and stacking conveyor of a sod harvester. The movement ofthe stacking head and/or the stacking conveyor can be controlled tomaximize the rate at which the stacking head can remove sod from thestacking conveyor. By maximizing this rate, a sod harvester can beoperated at increased speeds to produce higher yields.

In one embodiment, the present invention is implemented as a sodharvester that comprises a stacking conveyor configured to support oneor more slabs of sod prior to a stacking operation. The stackingconveyor is configured to rotate in a first direction to advance the oneor more slabs of sod. The sod harvester also comprises a stacking headconfigured to remove the one or more slabs of sod from the stackingconveyor as part of a stacking operation. The stacking head isconfigured to be positioned at at least two pick up positions overtopthe stacking conveyor with a first pick up position being closer to afront of the stacking conveyor than a second pick up position.

In another embodiment, the present invention is implemented as a sodharvester that comprises a stacking conveyor configured to support oneor more slabs of sod prior to a stacking operation. The stackingconveyor is configured to rotate in a first direction to advance the oneor more slabs of sod to a pick up position. The sod harvester alsocomprises a stacking head configured to remove the one or more slabs ofsod from the stacking conveyor at the pick up position as part of astacking operation and to stack the one or more slabs of sod at one ofat least two stacking positions. The stacking conveyor is configured toadvance the one or more slabs of sod to the pick up position at a ratethat is based on a particular stacking position at which the one or moreslabs will be stacked.

In another embodiment, the present invention is implemented as a methodof operating a stacking head of a sod harvester. The stacking head isconfigured to remove sod from a stacking conveyor in at least a firstand a second pick up position and to stack the sod in at least a firstand a second stacking position. The stacking head is positioned at thefirst pick up position to enable the stacking head to remove one or moreslabs of sod from the stacking conveyor. The stacking head is then movedfrom the first pick up position to the second stacking position toenable the stacking head to stack the one or more slabs. The stackinghead is then positioned at the second pick up position to enable thestacking head to remove another one or more slabs of sod from thestacking conveyor. Then, the stacking head is moved from the second pickup position to the first stacking position to enable the stacking headto stack the other one or more slabs.

In another embodiment, the present invention is implemented as stackinghead of a sod harvester that comprises a main body portion, a sodsecuring portion configured to remove sod from a stacking conveyor, andat least one arm that secures the sod securing portion to the main bodyportion via a pivoting connection. The sod securing portion isconfigured to rotate from a first position to a second position aroundthe pivoting connection and to remove the sod from the stacking conveyorduring the rotation from the first position to the second position.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings in which:

FIGS. 1A-1D illustrate a series of movements of a stacking head betweena pick up position and two different stacking positions;

FIGS. 2A-2D illustrate a series of movements of a stacking head betweentwo different pick up positions and two different stacking positions;

FIGS. 3A-3D illustrate how a stacking head can be positioned at twodifferent pick up positions;

FIGS. 4A-4D illustrate how a stacking conveyor can advance sod atdifferent rates depending on the stacking position where the sod will bestacked; and

FIGS. 5A-5C illustrate a pivoting stacking head in three differentpositions.

DETAILED DESCRIPTION

In this specification, a stacking head refers to the mechanism of a sodharvester that picks up sod and stacks it, whether the sod is in slabsor in rolls. The manner in which the stacking head picks up the sod isnot essential to the invention. For example, the stacking head maydescend to a stacking conveyor to pick up the sod, or the stackingconveyor may be lifted to elevate the sod towards the stacking head.Further, in some implementations, the stacking head may descend and thestacking conveyor may be lifted.

Also, in this specification, a stacking head can employ many differenttypes of structures and/or techniques for securing the sod. For example,a stacking head can include pivoting clamps that grab the sod (e.g. onopposite sides of a roll or by squeezing the blades of a slab),extending blades or sharp implements that pierce through the sod (e.g.nails that extend into opposing sides of a roll or that extend throughslabs at an angle), etc. Accordingly, a stacking head should not beconstrued as having any particular structure for securing sod to thestacking head during a stacking operation.

Further, in this specification, a stacking conveyor should be construedas any conveyor from which the stacking head picks up sod whether thesod is in slabs or in rolls. Although the figures illustrate a stackingconveyor that is horizontal, a stacking conveyor should also beconstrued as including conveyors that are inclined in any direction aslong as the stacking head removes sod from the conveyor as part of astacking operation.

A pick up position refers generally to the relative position of thestacking head with respect to the stacking conveyor when the stackinghead removes sod from the stacking conveyor. A stacking position refersgenerally to the relative position of the stacking head with respect toa pallet (or other support structure) when the stacking head releasessod onto the pallet for stacking.

The present invention is directed to various techniques that can beemployed on a sod harvester to improve pick up and stacking operations.In many cases, these techniques can be employed to enable the sodharvester to operate at higher speeds thereby increasing the rate atwhich sod is harvested.

These techniques include employing multiple pick up positions andoperating the stacking conveyor at variable speeds. In either case, thetechnique can be based on the fact that it may require different amountsof time to return the stacking head to a pick up position based on theprevious stacking position.

FIGS. 1A-1D provide a series of top views of a sod harvester toillustrate how a sod harvester may employ multiple stacking positions.In each of FIGS. 1A-1D, a stacking conveyor 102, a stacking head 103,and a pallet 110 is depicted with stacking head 103 moving between apick up position 112 (represented by the dashed box over stackingconveyor 103) and two different stacking positions 111 a and 111 b(represented by the dashed boxes over pallet 110). In these figures, itis assumed that sod travels from right to left on stacking conveyor 102.The arrows represent the movement of stacking head 103 from pick upposition 112 depicted in FIGS. 1A and 1C to stacking positions 111 a and111 b depicted in FIGS. 1B and 1D respectively. After stacking sod ineach of stacking positions 111 a and 111 b, stacking head 103 can returnto pick up position 112 to pick up more sod. Because stacking position111 a is farther from pick up position 112 than stacking position 111 b,it can require a greater amount of time for stacking head 103 to travelto stacking position 111 a than to stacking position 111 b.

Although FIGS. 1A-1D depict only two stacking positions, a stacking headmay be configured to stack sod in more than two stacking positions. Forexample, the '418 application describes a stacking head that can rotatein an r axis to enable stacking in at least four different stackingpositions. The techniques described below can be employed when anynumber of stacking positions are used.

The amount of time required for the stacking head to travel from pick upposition 112 to stacking position 111 b and then return to pick upposition 112 will be referred to as T₁. The amount of time required forthe stacking head to travel from pick up position 112 to stackingposition 111 a and then return to pick up position 112 will be referredto as T₂. Therefore, T₂ is greater than T₁. This may be the case even ifstacking head 103 is moved more quickly when travelling to stackingposition 111 a.

The rate at which sod is positioned for pick up will be referred to asT₃. For example, the sod harvester can be operated at a speed thatcauses sod to be ready for pick up every T₃ seconds. The maximum valuefor T₃ is determined by T₂. In other words, the sod harvester cannot beoperated at a rate that would cause sod to reach pick up position 112before stacking head 103 is ready to pick up the sod. Otherwise,stacking conveyor 102 may have to be stopped (or otherwise slowed) towait for stacking head 103. Slowing stacking conveyor 102 typically willalso require slowing or stopping the inclined conveyor that feeds sod tothe stacking conveyor. T₂ therefore is a primary factor in determininghow fast a sod harvester can be operated.

For example, if T₁ is 2 seconds and T₂ is 3 seconds, T₃ at best can beset to 3 seconds. In this example, the sod harvester would therefore beoperated at a rate that causes sod to be ready for pick up (e.g.positioned at pick up position 112) every 3 seconds. Therefore, each twostacking operations will be completed in 6 seconds at best even thoughthe stacking head is capable of completing two stacking operations in 5seconds. This time for completing two stacking operations will bereferred to as 2T₃. To summarize, the present invention is directed tovarious techniques for minimizing the total time required to perform twostacking operations (i.e. minimizing 2T₃) so that a sod harvester canproduce sod at a quicker rate.

Employing Multiple Pick Up Positions

In accordance with one or more embodiments of the present invention, astacking head of a sod harvester can be configured to move between twoor more different pick up positions. For example, a stacking head can beconfigured to return to a pick up position that is further back from thefront of the stacking conveyor thereby increasing the amount of timethat the stacking head can take to return to a pick up position. The useof multiple pick up positions can increase the overall rate at which sodcan be removed from the stacking conveyor.

FIGS. 2A-2D illustrate a series of top views of a sod harvester 200 thatare similar to FIGS. 1A-1D except that stacking head 203 employs twostacking positions 212 a and 212 b. It will be assumed that position 212a is the same as position 112.

By employing two stacking positions, stacking conveyor 202 may beallowed to operate at a slightly faster rate. In particular, using twopick up positions may not alter times T₁ or T₂ as described abovebecause stacking head 203 may move back and forth at the same rateregardless of which pick up position it is moving to. However, by movingstacking head 203 backwards to pick up position 212 b, the value of T₃can remain the same for one stacking operation, but be reduced for theother stacking operation.

As described above T3 represents the time required to position sod atposition 212 a (or 112). However, when stacking head is picking up frompick up position 212 b, stacking conveyor 202 must advance sod theadditional distance to position 212 b making T₃ higher in such cases. T₃for such cases may be equal to the normal T₃ described above (i.e. setto the value of T₂). As a result, T₃ will be lower when positioning sodat pick up position 212 a because it requires advancing stackingconveyor 202 a shorter distance. These different values for T₃ will bereferred to as T_(3a) and T_(3b) respectively. The total time forperforming two stacking operations will therefore be T_(3a)+T_(3b).Because T_(3a) can be equal to T₂, while T_(3b) can be lower than T₂,T_(3a)+T_(3b) can be lower than 2T₃.

This movement from position 212 a to position 212 b can occur at anytime while stacking head travels from overtop pallet 210 to overtopstacking conveyor 202. For example, with respect to the orientation ofFIGS. 2A-2D, stacking head 203 can move downward and leftward at thesame time after stacking sod on pallet 210. This simultaneous movementin both directions will allow stacking head 203 to reach position 212 bin the same amount of time as it would take to reach 212 a. The leftwardmovement may also occur while stacking head 203 is descending and/orwhile stacking conveyor 202 is ascending for pick up of sod.

In some embodiments, pick up positions 212 a and/or 212 b can be fixedor may be dynamically determined. In some embodiments, pick up positions212 a and/or 212 b can be calculated dynamically based on an estimatedtime when sod will be ready for pick up. For example, the amount of timerequired to stack sod may not always be the same. In such cases, the sodharvester can include functionality for determining where the mostoptimal pick up position may be and cause stacking head 203 to move tothat position. If stacking head 203 can return to pick up position 212 ain time to pick up the sod, it may do so. However, if moving stackinghead 203 to pick up position 212 b may allow for more efficientoperation (e.g. by not slowing or stopping stacking conveyor 202), itmay do so including, in some cases, calculating the most optimalposition for pick up position 212 b.

FIGS. 3A-3D provide an example of how multiple pick up positions can beemployed in an implementation that accumulates multiple slabs of sod 350on a stacking conveyor 302 prior to being picked up by a stacking head303. A suitable process for accumulating slabs of sod on stackingconveyor 302 is disclosed in the '402 application which is incorporatedby reference.

As more thoroughly described in the '402 application and as representedin FIGS. 3A-3D, stacking conveyor 302 can be configured to accumulate anumber of slabs of sod 350 near a front end of stacking conveyor 302. Inthis example, three slabs are accumulated, although any other suitablenumber could be accumulated for pick up. Also, the techniques of thepresent invention could be used when a single slab is picked up.

Once the appropriate number of slabs has been accumulated at the frontend of stacking conveyor 302, stacking conveyor 302 is advanced to causethe accumulated slabs to be positioned under stacking head 303 at anappropriate pick up position. FIG. 3A represents the moment whenstacking head 303 has just picked up slabs while positioned at a firstpick up position 312 a. To represent that stacking head 303 hastravelled to a stacking position to stack the sod, FIG. 3B does not showstacking head 303. FIG. 3B also shows that slabs of sod 350 are againbeing accumulated on stacking conveyor 302.

FIG. 3C represents that three slabs of sod 350 have again beenaccumulated and are being advanced into an appropriate pick up positionon stacking conveyor 302. FIG. 3C represents a case where stacking head303 is moved backwards to allow pick up from a second pick up position312 b. As described above, this movement to pick up position 312 b mayoccur for various reasons including to account for a larger distancethat stacking head 303 must travel to stack the sod that was picked upin FIG. 3A.

FIG. 3D illustrates that stacking head 303 has descended to stackingconveyor 302 to pick up sod in the second pick up position 312 b. Afterstacking the sod, stacking head 302 may return to pick up position 312 asuch as if stacking head will only have to travel to a nearer stackingposition to stack the sod.

Typically, stacking conveyor 302 is not stopped while stacking head 303removes the slabs from stacking conveyor 302. Because of this, stackinghead 303 must be in an appropriate pick up position at the correct timeto allow stacking head 303 to secure the slabs of sod and remove themfrom stacking conveyor 302. As stated above, in some embodiments, theappropriate pick up position can be dynamically determined based onwhere the slabs to be picked up will be when the stacking head 303 canreach a pick up position. In other words, the distance that stackinghead 303 should be moved backwards can be determined based on at leasttwo factors: (1) the speed at which stacking conveyor 302 is moving; and(2) the amount of time it will take to position stacking head 303 at anappropriate pick up position.

By allowing stacking head 303 to be moved backwards to a different pickup position, stacking conveyor 302 can be advanced at a rate even ifthat rate will cause the slabs to be advanced beyond the normal pick-upposition. In some cases, the rate at which stacking conveyor 302 isadvanced can be based on the need to advance a subsequent slab ontostacking conveyor 303 from inclined conveyor 304. For example, it may benecessary to advance slabs 350 to the pick-up position at a sufficientrate to ensure that the pick-up process has been completed in time for anext slab to be advanced onto stacking conveyor 302. This sufficientrate may require stacking head 303 to be moved backwards to ensureproper positioning for pick up.

More particularly, in some cases, the speed at which stacking conveyor302 is advanced to position slabs under stacking head 303 may be toohigh in comparison to the speed of inclined conveyor 304. For example,if the difference between the speeds of the two conveyors is too large,the next slab may be damaged (e.g. ripped) as stacking conveyor 302pulls it from inclined conveyor 304. To avoid this, stacking conveyor302 can be advanced at a sufficient rate so that the slabs are removedby stacking head 303 prior to the next slab being advanced onto stackingconveyor 302. Once the slabs are removed, stacking conveyor 302 can beslowed down to an appropriate speed for advancing the next slab ontostacking conveyor 302. Therefore, this ability to move stacking head 303to a different pick up position allows stacking conveyor 302 to beadvanced at different rates even if a particular rate would advanceslabs beyond the normal pick-up position.

Again using T_(3a) and T_(3b), T_(3a) can represent the amount of timerequired to position sod at pick up position 312 b while T_(3b) canrepresent the amount of time required to position sod at pick upposition 312 a. With the value of T_(3a) being set based on T_(2—)(orthe amount of time required to stack sod at a farther stackingposition), T_(3b) will be lower than T₂ resulting in a decrease in theamount of time required to perform two stacking operations and anincrease in the rate at which sod may be harvested. For example, ifT_(3a) is 3 seconds, T_(3b) may be 2.95 seconds yielding approximately a1% increase in yield.

Advancing Stacking Conveyor at Variable Speeds

In addition to or in place of the use of multiple pick up positions, thestacking conveyor can be advanced at variable speeds to increase theoverall rate at which sod is removed from the stacking conveyor.Referring again to the different times (T₁ and T₂) that it takes astacking head to complete a stacking operation, the speed at which thestacking conveyor is advanced can be increased so that the slowerstacking operation (i.e. the stacking operation that requires T₂ secondsor the more distant stacking operation) can be commenced sooner which inturn will ensure that the stacking head can return to a pick up positionsooner. If the stacking head returns to a pick up position sooner, theoverall rate at which sod can be removed will be increased.

Advancing the stacking conveyor at variable speeds also allows T₃ to bereduced for some stacking operations. In other words, by selectivelyincreasing the rate at which the stacking conveyor is advanced, sod willbe ready for pick up in a slightly lower amount of time. The amount oftime required to position sod in a pick up position when a slower rateis used to advance the stacking conveyor will be referred to as T_(3c).Likewise, the amount of time required to position sod in a pick upposition when a faster rate is used to advance the stacking conveyorwill be referred to as T_(3d). T_(3d) will therefore be lower thanT_(3c). As with the use of multiple pick up locations, T_(3c) can be setbased on T₂ so that the amount of time required to perform two stackingoperations (T_(3c)+T_(3d)) is less than 2T₃.

FIGS. 4A-4D illustrate how a stacking conveyor 402 can be advanced atdifferent rates based on where the next stacking position is. AlthoughFIGS. 4A-4D are based on the slab accumulation technique disclosed inthe '402 application, any technique which advances sod to a pick upposition can be modified as described herein so that sod is advanced atdifferent rates depending on where it will be stacked.

As is disclosed in the '402 application, a number of slabs can beaccumulated at a front end of a stacking conveyor. Then, once theappropriate number of slabs have been accumulated, the stacking conveyorcan be advanced so that the slabs are positioned in the appropriate pickup position to allow the stacking head to remove them from the stackingconveyor. As described above, the stacking head can travel to multipledifferent stacking positions with at least one of the stacking positionsrequiring a greater amount of time to reach than at least one otherstacking position.

FIGS. 4A and 4B represent the case where the slabs are going to bestacked at a stacking position that requires more time to reach (andreturn) such as, for example, a farther stacking position. The stackingoperation performed in FIGS. 4A and 4B can therefore represent T₂. FIGS.4C and 4D, on the other hand, represent the case where the slabs aregoing to be stacked at a stacking position that requires less time toreach (and return) such as, for example, a nearer stacking position. Thestacking operation performed in FIGS. 4C and 4D can therefore representT₁. Other examples of stacking positions that may require more time toreach include rotated positions versus non-rotated positions. Thetechniques described herein can be employed regardless of why onestacking position may require more time to reach than another.

In FIG. 4A, three slabs of sod 450 have been accumulated at the frontedge of stacking conveyor 402 and are therefore ready to be advanced toa pick up position. This time at which the slabs of sod are ready to beadvanced to the pick up position is denoted as t₀ in the timeline.Because the slabs 450 are going to be stacked at a farther stackingposition, stacking conveyor 402 can be advanced at a faster rate so thatthe slabs reach the pick up position at time t₀+x. Therefore, at timet₀+x, stacking head 403 can remove the slabs 450 from stacking conveyor402 for stacking at the farther stacking position.

In contrast, FIGS. 4C and 4D (which are otherwise identical to FIGS. 4Aand 4B) show that stacking conveyor 402 is advanced at a slower rate sothat the slabs 451 reach the pick up position at a time t₀+y, where y isgreater than x. Therefore, at time t₀+y, stacking head 403 can removethe slabs 451 from stacking conveyor 402 for stacking at the nearerstacking location.

Because x is lower than y, the stacking operation at the fartherstacking location will be commenced sooner (with respect to the time atwhich the slabs are accumulated and ready to be advanced) than thestacking operation at the nearer stacking location. Because the stackingoperation at the farther stacking location commences sooner, stackinghead 403 will return to the pickup up position sooner than it otherwisewould if stacking conveyor 402 had not been advanced at a faster rate.Therefore, stacking head 403 can be ready for the next stackingoperation more quickly. As such, inclined conveyor 404 can be operatedat a faster rate to deliver slabs to stacking conveyor 402 more quicklythereby increasing the rate at which sod can be harvested.

In other words, sod that is going to be stacked at the farther stackingposition can be delivered to the pick up position in T_(3d) seconds.Assuming T_(3d) is 2.95 seconds and T₁ is 2 seconds, the stacking headcan easily be in position to pick up the sod within the 2.95 secondsbecause it will be returning from the nearer stacking position. Incontrast, sod that is going to be stacked at the nearer stackingposition can be delivered to the pick up position in T_(3c) seconds.Assuming T_(3c) is 3 seconds and T₂ is 3 seconds, the stacking head willreturn from the farther stacking position just in time to pick up thesod.

By selectively advancing stacking conveyor 402 at a faster rate,performance can be increased without increasing power consumption andwear that would otherwise occur if the stacking conveyor were alwaysadvanced at the faster rate. For example, advancing the stackingconveyor at the faster rate when the slabs will be stacked at the nearerstacking position may not provide any performance increases since thestacking head may be able to return from the nearer stacking position intime regardless of the rate. For example, using the numbers from theprevious paragraph, the stacking head can complete the stackingoperation at the nearer stacking position in 2 seconds which is wellwithin the 2.95 seconds that it will take until the sod is again readyto be picked up. Therefore, advancing the stacking conveyor at thefaster rate in such cases may waste power and increase wear without anyperformance benefits. Accordingly, the present invention can increaseharvesting yields in an efficient manner by only advancing the stackingconveyor at the faster rate when it will decrease the amount of time toperform a stacking operation.

Also, the present invention encompasses embodiments where the stackingconveyor is advanced at different rates and the stacking head employsmultiple pick up positions. For example, in FIGS. 4C and 4D, stackinghead 403, in contrast to what is shown, may be positioned at a differentpick up position (e.g. pick up position 312 b). In this way, afterstacking at the farther stacking position, stacking head 403 may returnto a pick up position further back on stacking conveyor 402 furtherincreasing the rate at which inclined conveyor 404 can deliver sod tostacking conveyor 402.

In terms of T₃, T_(3b) can be further reduced by advancing the stackingconveyor at a faster rate. For example, when picking up at pick upposition 312 a, the stacking conveyor can be advanced at the faster rateso that the pick up occurs sooner. Using the example numbers from above,T_(3b) can be further reduced to 2.9 seconds by advancing the stackingconveyor at the faster rate. In such cases, T_(3a) may remain 3 secondsto accommodate for the value of T₂ of 3 seconds.

In any of the described embodiments, various combinations of softwareand hardware can be employed to determine when to move the stacking headto a different pick up position, when to advance the stacking conveyorat a different rate, etc. For example, sensors may be employed to detectthe position of the stacking head, the position of sod, or anotherfactor that can be used to determine when or whether to implement thetechniques described above.

Although the above description has used examples where only two stackingpositions are employed, the described techniques can be employed whenmore than two stacking positions are used even if each stacking positionrequires a different amount of time to perform a stacking operation. Insuch cases, the pick up position and/or the rate at which the stackingconveyor is advanced can be controlled based on a particular stackingposition.

Pivoting Stacking Head

FIGS. 5A-5C illustrate a pivoting stacking head 500 that can be employedon a sod harvester. Pivoting stacking head 500 can, but is not requiredto, be used in conjunction with any of the above described techniques.

In preferred embodiments, pivoting stacking head 500 can be used whenthe stacking conveyor is not stopped to allow the stacking head to pickup sod. Pivoting stacking head 500 can therefore be used in theembodiments described in the '402 application.

Pivoting stacking head 500 comprises a main body portion 504 to which asod securing portion 501 is connected via arms 502 and 503. Main bodyportion 504 can be configured to secure stacking head 500 to a supportframe (not shown) along which stacking head 500 can traverse to movebetween a pick up position and a stacking position. Arms 502 and 503 areconnected to main body portion 504 via pivoting connections 502 a and503 a respectively. Similar pivoting connection may also be used betweenarms 502 and 503 and sod securing portion 501 to ensure that sodsecuring portion 501 remains substantially horizontal during movement.

Pivoting connections 502 a and 503 a allow sod securing portion 501 tobe swung along an arc from a first position (shown in FIG. 5A) to asecond position (shown in FIG. 5C). Sod securing portion 501 can be inthe first position prior to picking up sod from a stacking conveyor.Then, as shown in FIG. 5B, sod securing portion 501 can be allowed todrop (or rotated via a motor) towards the stacking conveyor. Because ofpivoting connections 502 a and 503 a, sod securing portion 501 will droptowards the stacking conveyor along an arc (e.g. following a downwardand a rightward trajectory based on the orientation shown in FIGS.5A-5C).

As sod securing portion 501 drops towards the stacking conveyor, hooks501 a (or other securing means) may extend to pierce or otherwise securesod on the stacking conveyor to allow stacking head 500 to pick up thesod. Next, continued rotation about pivoting connections 502 a and 503 acause sod securing portion 501 to elevate upward towards main bodyportion 504 to the second position thereby lifting the sod from thestacking conveyor. Hooks 501 a remain extended until stacking head 500travels to an appropriate stacking position where the hooks can bewithdrawn releasing the sod.

Sod securing portion 501 can be configured to return to the firstposition prior to stacking the sod (e.g. immediately after removing sodfrom the stacking conveyor) or may stack the sod while in the secondposition and then return to the first position. In other embodiments,sod securing portion 501 can be configured to stack the sod in eitherthe first or the second position.

Because of the swinging motion enabled by pivoting connections 502 a and503 a, sod securing portion 501 can be moved between the first positionand the second position using relatively little energy. In other words,the design of pivoting stacking head 500 can take advantage of gravityto perform a sod pick up operation. In some embodiments, pivotingconnection 502 a can include a motor for controlling the motion of sodsecuring portion 501. This motor can control when sod securing portion501 is released from the first position and returned to the firstposition. The motor can also supply sufficient energy to ensure that sodsecuring portion 501 fully reaches each position. In embodiments wherepivoting connection 502 a includes a motor, pivoting connection 503 amay not include a motor and may serve to provide stability.Alternatively, pivoting connection 503 a may include a motor andpivoting connection 502 a may serve to provide stability.

In some embodiments, the first position can be a forward position suchthat the movement of sod securing portion 501 from the first position tothe second position is in the same direction as the movement of sod onthe stacking conveyor. In such cases, sod would move from left to rightalong the stacking conveyor in the example shown in FIGS. 5A-5C. Bymoving in the same direction as the stacking conveyor, sod securingportion 501 can more efficiently remove sod from the stacking conveyor.For example, this movement with the stacking conveyor reduces therelative speed of the sod with respect to stacking head 500. Thisreduced relative speed facilitates removal of the sod even if thestacking conveyor is operating at relatively high speeds.

In some embodiments, in addition to the movement of sod securing portion501 from the first position to the second position, main body portion504 may also be configured to move in an opposite direction. In otherwords, while sod securing portion 501 swings from the first position tothe second position, main body portion 504 (and as a result, sodsecuring portion 501) can move in an opposite direction. With referenceto FIGS. 5A-5C, this opposite movement may be from right to left. Theopposing movement of main body portion 504 can be employed to reduce thespeed of sod securing portion 501 with respect to the stacking conveyorwhich may be desirable in some cases to smooth the overall operation ofthe stacking head.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed:
 1. A sod harvester comprising: a stacking conveyorconfigured to support one or more slabs of sod prior to a stackingoperation, the stacking conveyor configured to rotate in a firstdirection to advance the one or more slabs of sod; and a stacking headconfigured to remove the one or more slabs of sod from the stackingconveyor as part of a stacking operation, wherein the stacking head isconfigured to be positioned at at least two pick up positions overtopthe stacking conveyor with a first pick up position being closer to afront of the stacking conveyor than a second pick up position.
 2. Thesod harvester of claim 1, wherein the stacking head is configured tostack the one or more slabs of sod at at least two stacking positions,and wherein the stacking head is positioned at the first pick upposition after stacking the one or more slabs of sod at the firststacking position, and the stacking head is positioned at the secondpick up position after stacking the one or more slabs of sod at thesecond stacking position.
 3. The sod harvester of claim 2, wherein agreater amount of time is required to stack sod at the second stackingposition than at the first stacking position.
 4. The sod harvester ofclaim 2, wherein the second stacking position is farther from thestacking conveyor than the first stacking position.
 5. The sod harvesterof claim 2, wherein the stacking head is configured to rotate to reachat least one of the at least two stacking positions.
 6. The sodharvester of claim 1, wherein the stacking conveyor is configured toadvance the one or more slabs of sod to the at least two pick uppositions using at least two different rates.
 7. The sod harvester ofclaim 1, wherein the stacking conveyor advances the one or more slabs ofsod to the first pick up position at a faster rate than the stackingconveyor advances the one or more slabs of sod to the second pick upposition.
 8. The sod harvester of claim 7, wherein the stacking head isconfigured to stack the one or more slabs of sod at at least twostacking positions, and wherein the stacking head is positioned at thefirst pick up position after stacking the one or more slabs of sod atthe first stacking position, and the stacking head is positioned at thesecond pick up position after stacking the one or more slabs of sod atthe second stacking position.
 9. The sod harvester of claim 1, whereinthe stacking head includes a pivoting connection that allows at least aportion of the stacking head to descend along an arc to remove the oneor more slabs of sod from the stacking conveyor.
 10. A sod harvestercomprising: a stacking conveyor configured to support one or more slabsof sod prior to a stacking operation, the stacking conveyor configuredto rotate in a first direction to advance the one or more slabs of sodto a pick up position; and a stacking head configured to remove the oneor more slabs of sod from the stacking conveyor at the pick up positionas part of a stacking operation and to stack the one or more slabs ofsod at one of at least two stacking positions; wherein the stackingconveyor is configured to advance the one or more slabs of sod to thepick up position at a rate that is based on a particular stackingposition at which the one or more slabs will be stacked.
 11. The sodharvester of claim 10, wherein the at least two stacking positionsinclude a first stacking position and a second stacking position, andwherein a greater amount of time is required to stack the one or moreslabs of sod at the second stacking position than at the first stackingposition, the stacking conveyor advancing the one or more slabs of sodto the pick up position at a faster rate when the one or more slabs ofsod will be stacked at the second stacking position.
 12. The sodharvester of claim 10, wherein the second stacking position is fartherfrom the stacking conveyor than the first stacking position.
 13. The sodharvester of claim 12, wherein the pick up position comprises at leasttwo pick up positions with a first pick up position being closer to afront of the stacking conveyor than a second pick up position, andwherein the stacking head is positioned at the first pick up positionwhen the stacking conveyor is advanced at the faster rate.
 14. The sodharvester of claim 10, wherein the stacking head includes a pivotingconnection that allows at least a portion of the stacking head todescend along an arc to remove the one or more slabs of sod from thestacking conveyor.
 15. A method of operating a stacking head of a sodharvester, the stacking head being configured to remove sod from astacking conveyor in at least a first and a second pick up position andto stack the sod in at least a first and a second stacking position, themethod comprising: positioning the stacking head at the first pick upposition to enable the stacking head to remove one or more slabs of sodfrom the stacking conveyor; moving the stacking head from the first pickup position to the second stacking position to enable the stacking headto stack the one or more slabs; positioning the stacking head at thesecond pick up position to enable the stacking head to remove anotherone or more slabs of sod from the stacking conveyor; and moving thestacking head from the second pick up position to the first stackingposition to enable the stacking head to stack the other one or moreslabs.
 16. The method of claim 15, wherein the first pick up position iscloser to a front of the stacking conveyor than the second pick upposition.
 17. The method of claim 15, wherein a greater amount of timeis required to move the stacking head to the second stacking positionthan to the first stacking position.
 18. The method of claim 15, whereinthe second stacking position is farther from the stacking conveyor thanthe first stacking position.
 19. The method of claim 15, furthercomprising: operating the stacking conveyor at a first rate to advancethe one or more slabs of sod to the first pick up position; andoperating the stacking conveyor at a second rate to advance the otherone or more slabs of sod to the second pick up position, the first ratebeing faster than the second rate.
 20. A stacking head of a sodharvester comprising: a main body portion; a sod securing portionconfigured to remove sod from a stacking conveyor; and at least one armthat secures the sod securing portion to the main body portion via apivoting connection such that the sod securing portion is configured torotate from a first position to a second position around the pivotingconnection, the sod securing portion configured to remove the sod fromthe stacking conveyor during the rotation from the first position to thesecond position.
 21. The stacking head of claim 20, wherein the firstposition is closer to a front of the stacking conveyor than the secondposition.
 22. The stacking head of claim 21, wherein the main bodyportion is configured to move in a horizontal direction towards thefront of the stacking conveyor while the sod securing portion rotatesfrom the first position to the second position.
 23. The stacking head ofclaim 20, wherein the sod securing portion rotates back from the secondposition to the first position prior to stacking the sod.
 24. Thestacking head of claim 20, wherein the stacking head is configured toremove sod from the stacking conveyor in at least two pick up positionswith a first pick up position being closer to a front of the stackingconveyor than a second pick up position.
 25. The stacking head of claim24, wherein the stacking head is configured to stack sod in at least afirst stacking position and a second stacking position, and wherein agreater amount of time is required to move the stacking head to thesecond stacking position than than to first stacking position, andwherein the stacking head is positioned in the second pick up positionafter stacking sod at the second stacking position.